1. Technical Field
This invention relates generally to voltage comparator circuity and, more particularly, to a voltage comparator circuit operable for providing successive voltage window detection.
2. Discussion
Voltage comparator circuits are available in many configurations and are employed for a wide variety of uses. Generally speaking, the basic comparator circuit compares an input voltage with a voltage threshold and produces an output voltage or current indicative of the voltage comparison. A voltage window comparison can be accomplished with two voltage comparator circuits to determine if an input voltage has an amplitude within a window defined by two threshold voltages. A typical voltage window comparator circuit includes a first comparator for comparing the input voltage to a first voltage threshold and a second comparator for comparing the input voltage with a second voltage threshold. The output of the first and second comparators are logically ANDed together to determine if the input voltage is within the voltage window bounded by the first and second voltage thresholds.
For some applications, it may be desirable to determine whether an input voltage is within one of several successive voltage windows. In doing so, an array of successive comparators can be connected to a common input voltage, each comparator designed to respond to a distinct reference voltage. To realize successive voltage windows, an array of interconnected comparators, inverters and AND gates could be used. For example, given lower, middle and upper voltage boundaries which define two voltage windows, three comparators could be employed to compare an input voltage with each voltage boundary. That is, a first comparator for comparing the lowest boundary with the input voltage, a second comparator for comparing the middle boundary with the input voltage and a third comparator for comparing the upper boundary with the input voltage. The output of the first comparator could be inverted and logically ANDed with the output of the middle comparator to provide an output which is indicative of the input voltage being within the window bounded by the lowest and middle voltages. Likewise, the output of the second comparator could be inverted and logically ANDed with the output of the third comparator to provide an output which is indicative of the input voltage being within the window bounded by the middle and upper voltages.
According to this configuration, N continuous voltage window comparisons could be accomplished, where 2N +1 comparators would generally be required. While the above-mentioned voltage window comparator circuit could be employed to provide successive voltage window detection, a relatively large number of comparators are required. Accordingly, the large number of comparators adds to the overall size and cost of the circuitry.
It is therefore desirable to provide for a voltage window comparator circuit and method for comparing an input voltage with voltage windows in a manner which requires a minimum number of components.
More particularly, it is desirable to provide for a voltage window comparator circuit and method for comparing a voltage input with successive voltage windows and with relatively few comparators to provide a simplified digital output.
It is further desirable to provide for such a voltage window comparator circuit and method for providing a digital output based on a comparison of successive voltage windows to accomplish voltage decoding for memory addressing.